Conventionally, as a coating apparatus for carrying out coating over a body of a car, for example, an electrostatic coating apparatus for an electrically conductive coating material is known. In the electrostatic coating apparatus for an electrically conductive coating material, a high voltage is applied to the electrically conductive coating material supplied to a coating gun. Therefore, it is necessary to prevent a current from leaking out of a coating material supplying path for supplying the coating material to the coating gun. For this reason, an insulating and separating valve for temporarily dividing the coating material supplying path to bring an electrical insulating state is provided in the coating material supplying path (see Patent Documents 1 and 2). In other words, in electrostatic coating, the insulating and separating valve electrically insulates and separates the coating material supplying path into an application side in which a high voltage is applied and the other non-application side. Consequently, the current is prevented from leaking in the coating. On the other hand, the coating material supplying path including the insulating and separating valve is connected in the supply of the coating material to the coating gun. Thus, the coating material can be supplied.
In order to remove the coating material left in the insulating and separating valve in a proper timing between the supply of the coating material and the electrostatic coating, moreover, a cleaning fluid is supplied to the insulating and separating valve so that the insulating and separating valve is cleaned. Then, an air blow is carried out over the insulating and separating valve in order to dry the cleaning fluid.
In the conventional electrostatic coating apparatus, however, it is necessary to carefully carry out the air blow because there is a possibility that the cleaning fluid might be left on the application side. The cleaning fluid left on the application side might cause the leakage of the current in subsequent coating. Under the circumstances, therefore, plenty of time is required for the air blow.
When the coating material supplying path is to be cleaned with the cleaning fluid, moreover, a discharge or a heat generation is caused in a connecting part of the insulating and separating valve if the insulating and separating valve is connected in a state in which an electric charge is left on the application side. Therefore, there is a possibility that the connecting part might be broken, resulting in a reduction in a sealing force. For this reason, it is necessary to remove the residual electric charge from the application side of the coating material supplying path before the insulating and separating valve is connected after the electrostatic coating is carried out. In the conventional electrostatic coating apparatus, however, waiting is carried out until the residual electric charge is spontaneously discharged from the application side. Therefore, it is impossible to rapidly start the work for cleaning the coating material supplying path after performing the electrostatic coating.
In the connecting device described in Patent Document 1, moreover, the cleaning solution is supplied in the state in which the insulating and separating valve is connected. For this reason, there is a possibility that the cleaning solution cannot be supplied to the part in which the member on one of the sides of the insulating and separating valve and the member on the other side come in contact with each other and the coating material might be thus left.
On the other hand, in the connecting device described in Patent Document 2, two cylinders for generating thrusts in opposite directions to each other are used to form a clearance between the member on one of the sides of the insulating and separating valve and the member on the other side when the cleaning solution is to be supplied. More specifically, a necessary clearance for the cleaning is formed by causing both of the members to approach each other through one of the cylinders and separating them from each other through the other cylinder in the cleaning. In the connecting device, however, a pressure of the cleaning solution to be supplied to the clearance between both of the members is not considered in detail. For this reason, when the cleaning solution is supplied, the member is pushed back by the pressure of the cleaning solution so that the cleaning solution leaks. As a result, there is a possibility that a cleaning failure might be caused.